The present invention relates to decompression data display devices which calculate inert gas partial pressures in the tissues of the body of a diver different in half saturation time during diving, and obtain and display data for a non-decompression dive or a decompression dive from the inert gas partial pressures.
When a diver stays or stops at a position deeper than a particular water depth for more than a given amount of time, he requires a decompression operation in which he stays for a predetermined amount of time at a designated depth so as to avoid suffering from caisson disease when he rises to the surface of the water.
In order to accurately calculate the decompression depth and time for the decompression operation, it is necessary to accurately know inert gas partial pressures solved in the respective tissues of the diver's body.
To this end, decompression data display devices have been invented which calculate the amounts of nitrogen in the respective tissues of the body of a diver during diving on a real time basis, and obtain and display data for appropriate decompression from the calculated amounts of nitrogen, as disclosed in U.S. Pat. Nos. 4,005,282, 4,192,001, 4,054,783, 4,782,338, and 5,049,864, and U.S. patent application Ser. No. 07/976,399 (now U.S. Pat. No. 5,351,188) whose inventor is the same as the present inventor.
Those devices classify the tissues of the diver's body in accordance with a half saturation time, which is the time required for an amount of nitrogen solved or discharged into or from a tissue to reach 50% of its saturated amount, in consideration of the fact that the rates of solution or discharge of nitrogen into or from the respective tissues of the diver's body vary from tissue to tissue, calculate nitrogen partial pressures in the respective tissues of the diver's body, using data on the half saturation time, etc., calculate data for a non-decompression or decompression dive from the nitrogen partial pressures and a safety limit nitrogen partial pressure and display that data.
There is, however, the problem that since the nitrogen partial pressures in the tissues cannot be calculated with high accuracy in the conventional decompression data display devices, accurate decompression data cannot be obtained.
Thus, decompression data must be calculated and displayed in consideration of enough safety. Therefore, if, for example, the remaining time until the non-decompression limit is to be calculated from the nitrogen partial pressures in the respective tissues and displayed, the device can display that there is no remaining time until the non-decompression limit although there is enough such time actually, thereby reducing the dive time.